Wednesday, May 1, 2013

The end of the semester is in sight!

Well, the semester is almost over and I can't wait.  I have two ~20 page papers to write by May 7th, one presentation to give, and one final on May 14th.  After that I can set my sights back on making some serious headway with Creeky.  However, despite my efforts to focus on school and work, Creeky keeps creeping into my train of thought.  It's kind of a problem.  Where I intend to spend 5-10 minutes researching things online between homework assignments or meetings I end up spending at least an hour.  I'm just trying to put some dots together in my head so that when my schedule opens up I have an action plan to complete projects rather than taking more measurements and spending more time researching things online.

The main thing I have been researching is the engine and drivetrain configuration.  To recap, the issue I am having is that when the transmission is in forward the thrust is in reverse.  Right now I am chasing down as much literature as I can find on the various components involved (see below).  I have managed to find quite a bit of information on just about everything except for the controllable pitch prop system, which is Norwegian.  I have emailed West Mekan a few times, but have not received a response to date.  I plan to call them tomorrow morning.

Engine: Westerbeke W80
Transmission: Velvet Drive C71 (Model 10-17-004, Ratio 1:1) 
both of these are reverse mounted with a driveshaft going into an independently mounted V-Drive
V-Drive: Walter RV-20 (Ratio 2.56:1) 
which goes into a controllable pitch prop
Prop: West Mekan AS Type 40 HV3 Controllable Pitch Prop System

What I know so far is that looking from the stern of the boat the engine rotates in the RH direction.  When the transmission is in forward the driveshaft going into the V-Drive also rotates in the RH direction.  This is reversed by the V-Drive and the output of propshaft is in the LH rotation.  From what little bit of information I have been able to find online about the West Mekan system it appears that the prop is likely a RH prop.  I have tried adjusting the pitch of the prop all the way in both directions, but it does not go past the feathered position to allow a reversal of the thrust while maintaining the same rotational direction.

It seems like the issue may be that the V-Drive is the incorrect model (they made the same model with an idler gear to keep the rotational direction) or the prop is incorrect.  However it seems extremely unlikely that Henry (the original owner of the boat) would have made such an oversight given all the thought he put into everything else.  Another possibility is that when the prop was installed the blades were put on facing the wrong direction, but I don't even know if that is possible.  Since the prop is underwater, this is the one thing I can't visually diagnose, at least not easily.  A final possibility is that everything is correct and I just need to use the reverse gear to obtain forward motion, but I am almost certain that is not the case.  From what I have read this will kill the transmission in a hurry, but there are a few sources that also disagree with this.

What I really need is a free weekend to really go through all of the possibilities while I am on the boat!  For now I will just have to keep digging for more info and try to be patient, which is not one of my strong suits.

It doesn't help my brain that the prop is feathered in this picture because I don't know which way the blades rotate.

2 comments:

  1. Study first. Work on the boat later. There is plenty of time to solve the mystery of the V-drive after exams. That being said, while you are writing your papers, consider this: What if the V-drive is designed to turn the shaft in one direction only? Suppose the thrust (forward and reverse) is intended to be controlled by the pitch of the prop (kind of like the old C-130 aircraft. They are able to go forward and backward with the same rotation of the engines. I recall how uncanny it was to see the pilots backs these planes up just like automobiles...) Just a thought, is all....

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  2. The controllable pitch prop is not designed to go far enough to provide reverse thrust, it just goes far enough to feather to reduce drag for cruising. Forward and reverse are controlled by the transmission.

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